Conventional organ printing technology (ink-jet printing) makes it possible to place viable cells in a three dimensional architecture. See, e.g., U.S. Pat. No. 7,051,654. And, various cells can be concurrently printed in an accurate manner. Because a tissue/organ has a complex structure, the organ printing technology is the most promising potential technology to mimic the anatomical structure of tissues or organs.
However, with ink-jet cell printing techniques, the material being processed must be a low viscosity gel. As a result, high aspect ratio structures, or porous structures that facilitate the transport of nutrient and oxygen into the construct, cannot easily be achieved. This is because the low viscosity materials being printed have relatively low mechanical stability. In addition, the printing materials are easily deformed in liquid by swelling or shrinkage. Hence, after implantation of tissue engineered scaffolds made by organ printing, it is difficult to preserve the pre-defined shape of the structure and protect immature cells or tissue therein.
The production of living organs and tissues by injection molding of forms generated by CAD/CAM has been described, but such methods again make the preservation of pre-defined shapes difficult. See, e.g., U.S. Pat. No. 6,773,713.
Accordingly, there is a need for new techniques for generating tissues, tissue scaffolds, and organs containing live cells for implantation.